1. Field of the Invention
The present invention relates to a rotary connector device equipped with a built-in steering angle sensor in which a steering angle sensor detecting a rotational angle of the steering wheel in a vehicle and a rotary connector used in the steering wheel are integrated, particularly for obtaining a small-sized rotary connector device equipped with a built-in steering angle sensor.
2. Related Art
A steering wheel of a vehicle is provided with a horn and audio control switches etc. Further, a number of vehicles in which a steering wheel equipped with an airbag for absorbing shocks in a crash are being increased. A vehicle is equipped with a rotary connector having a rotary side rotating with the steering wheel and a stationary side not rotating that are connected with a flexible flat cable (FFC), in order to maintain electric connection of parts disposed in the steering wheel with the car body even while the steering wheel rotates.
Further, recently, as vehicles become intelligent, vehicles that allow adjustment of driving control according to operational angles of a steering wheel in traveling have been on the market. Such vehicles are equipped with a steering angle sensor to detect rotational angles of the steering wheel.
JP-A-2000-159037 discloses a rotary connector device equipped with a built-in steering angle sensor manufactured thin by integrating the steering angle sensor and a rotary connector.
FIG. 5 is a schematic view of the above-mentioned device. The device includes a rotary connector 20, an FFC 27, a rotary connector-stationary cover 23 providing a space for the FFC 27, a lower stationary cover 21, a rotary cover 22 rotating with a steering wheel 10, and a circuit board 24. Further, a steering angle sensor 30 includes an annular driving gear 38 rotating with the steering wheel 10, a driven-gear 39 rotating by meshing with the annular driving gear 38, a circuit board 41 equipped with a rotational detecting element for the driven-gear 39, and a lower stationary cover 21 for the rotary connector 20 and a steering angle sensor-lower stationary cover 37 that provide a space for the parts.
The FFC 27 has a large-diameter winding portion 271 that is formed counterclockwise around the outer wall of the rotary connector-stationary cover 23, a small-diameter winding portion 272 that is formed clockwise around the cylindrical portion of the rotary cover 22, and a reverse portion that reverses the winding direction of the large-diameter winding portion 271 and the small-diameter winding portion 272. The end of the large-diameter winding portion 271 is connected to a connector 26 of the rotary connector-stationary cover 23 and the end of the small-diameter winding portion 272 is extended through a through-hole of the rotary connector-stationary cover 23 and connected to a circuit board 24. Further, the end of the small-diameter winding portion 272 is electrically connected to a connector 25 of the rotary cover 22 through the circuit board 24.
As the steering wheel 10 rotates and the rotary cover 22 correspondingly rotates, the small-diameter winding portion 272 of the FFC 27 is rotated together with the rotary cover 22. With the small-diameter winding portion 272 rotating, the large-diameter winding portion 271 of the FFC 27 is fixed with the rotary connector-stationary cover 23. The rotation of the steering wheel 10 is absorbed by movement of the reverse portion and an electric passage formed by the connector 26, FFC 27, circuit board 24, and connector 25 are maintained.
The configuration of the steering angle sensor 30 is shown in detail in FIG. 6. FIG. 6 is an exploded perspective view of each part of the steering angle sensor 30 upside down, seen from below.
In the steering angle sensor 30, as the steering wheel 10 rotates, the annular driving gear 38 rotates, the driven-gears 39, 40 rotate, and magnets fixed to the driven-gears 39, 40 correspondingly rotate. Changes in the magnetic fields due to the rotation of the magnets are detected by the circuit element of the circuit board 41 and rotational angle information of the steering wheel 10 is transferred to the connector 62 of the steering angle sensor-lower stationary cover 37 through the circuit board 41.
To reduce the size and thickness of the rotary connector device equipped with a built-in steering angle sensor, the number of parts is reduced by sharing the lower stationary cover 21 for the rotary connector 20 as the upper housing for the steering angle sensor 30.
It is preferable to reduce the size as much as possible of a rotary connector device equipped with a built-in steering angle sensor attached to a steering wheel to supply flexibility in design around a driver's seat.
However, a rotary connector device equipped with a built-in steering angle sensor in the related art has two circuit boards 24, 41 for a rotary connector and a steering angle sensor, respectively, so that it was difficult to reduce the size and thickness.